Influences of a flat plane splint on neural tone

Could someone at PRI explain how a flat plane splint changes neural tone that results in an inhibition of accessory breathing muscles, brachial chain and AIC? I have observed a marked improvement in the ability of person to achieve inhibition of these chains and facilitation for diaphragm breathing with posterior mediastinal expansion when the splint is in place.

Any mouth appliance or oral orthotic will impact or influence sensory input that the brain receives from occlusal references. By reducing or changing familiar contact references from cusps or surfaces of teeth, that are associated with specific neural tension of the musculature of the head and neck, an individual, who is patterning respiratory function around the cervical-cranial neural tension, will have to discover new reference points for respiratory function. If diaphragmatic position is not ideal at both attachment sites on the ribs and thoraco-lumbar spine and sensory reference from the floor, pelvis and hips is unilateral at the time the oral splint or orthotic is applied, demands and tension on the visual system and other sensory organs, tongue, temporal bone for hearing, etc. will more than likely increase. Accessory respiration is a volitional event and should remain this way if thoracic reference and expansion is sensed upon inhalation during tongue up and teeth apart function. A forward, thrusting tongue and above normal static contact are indicators of bruxing, trismic or clenching behavior as a result of dependency on the accessory respiratory system, because of limited sense of thoracic expansion secondary to the neurologic hyperventilatory state that co-exists. By allowing the mandible or neck to shift or move and become ‘unstable’, the referenced “pull” for this accessory respiratory function is now eliminated and the need to establish more moderate level of forward bending position, of the thorax is created. Thus, better relaxation of all accessory muscles of respiration and better mechanical advantage of both the hemi-diaphragms of the thorax also occurs. 

– Ron Hruska